Directional drilling apparatus

ABSTRACT

As a preferred embodiment of the invention disclosed herein, a new and improved tool carrying a drill bit on its lower end is dependently coupled from a drill string and lowered into a borehole which is to be excavated along a selected axis. One or more pressure-responsive wall-engaging members are operatively arranged on the tool in such a manner that, when correctly oriented and actuated, the drill bit will be diverted in a desired lateral direction. Pressure-actuated control means are arranged on the tool for selectively extending the wall-engaging members in response to deliberate changes in the circulating pressure.

United States Patent 2,876,992 3/1959 Lindsay 3,043,381 7/1962McNee1y,Jr.

ABSTRACT: As a preferred embodiment of the invention disclosed herein, anew and improved tool carrying a drill bit on its lower end isdependently coupled from a drill string and lowered into a boreholewhich is to be excavated along a selected axis. One or morepressure-responsive wall-engaging members are operatively arranged onthe tool in such a manner that, when correctly oriented and actuated,the drill bit 'will be diverted in a desired lateral direction.Pressure-aetuated control means are arranged on the tool for selectivelyextending the wall-engaging members in response to deliberate changes inthe circulating pressure.

PATENTEU JuLemn SHEET 2 [IF 2 Jackson R. C laycomb INVENTOR ATTORNEY 2DIRECTIONAL DRILLING APPARATUS In drilling an oil well, it is well knownthat variations in the weight applied to the drill bit, the rotativespeed, and the rotative direction will often inadvertently deviate theborehole from its intended axis. On the other hand, in many drillingoperations it may be necessary to drill a deviated borehole having adesired inclination as well as a selected azimuthal orientation. In suchsituations, the drill bit is deliberately diverted so as to pass aborehole obstruction or to reach a specified target area that is at aconsiderable depth and horizontal displacement from the drilling rig atthe surface.

It has been the usual practice heretofore to employ socalled whipstock"tools or the like for either deviating a borehole toward a desiredlocation or returning it to an intended axis. Some typical whipstocktools include a wedgelike body that is slidably mounted on the drillstring and has an inclined longitudinal face. Once this slidably mountedbody is positioned in a desired orientation along one side of theborehole, a small-diameter drill bit on the drill string is advanceddownwardly along the inclined face of the body and diverted accordinglyin a desired direction and inclination to excavate a reduced-diameterpilot hole for some distance into the formation. The whipstock andsmaller drill bit are removed from the borehole and a full-sized bit isthen run in on the drill string to enlarge or ream the smaller pilothole. This operation is repeated as many times as is necessary toaccomplish the desired job.

To avoid such time-consuming whipstocking operations, other tools havealso been employed which generally include an assembly having one ormore manually positioned deflecting members arranged thereon. Once thesedeflecting members are secured in a desired configuration at thesurface, the assembly is run into the borehole immediately above thedrill bit. Then, once the tool assembly has been properly oriented fromthe surface, drilling is commenced and the fixed deflecting members willhopefully divert the drill bit along a desired axis. It will beappreciated,.however, that with even such improved tools, the directionand inclination of the borehole must be frequently checked; and, if itis discovered that the borehole is not being deviated properly, theassembly must be returned to the surface for making correctiveadjustments. It is readily apparent, of course, that even an infrequentreturn of the drill string and tool assembly to the surface for suchadjustments constitutes a time-consuming and, therefore, an expensiveoperation. 7

Accordingly, it is an object of the present invention to provide new andimproved apparatus for selectively guiding a drill bit as itprogressively excavates a borehole without it being necessary to removethe drill string from the borehole during the course of the drillingoperation for making corrective adjustments to the guiding apparatus.

This and other objects of the present invention are attained byproviding a directional well-drilling tool having pressureactuatedguiding means operatively mounted above the drill bit and adapted fordeflecting the drill bit along selected axes of excavation. To operatethe guiding means, pressure-responsive control means are arranged on thetool in such a manner that operation of the guiding means is effectivelyaccomplished simply by selectively varying the pressure of the drillingfluids flowing through the drill string.

The novel features of the present invention are set forth withparticularlity in the appended claims. The invention, together withfurther objects and advantages thereof, may be best understood by way ofthe following description of exemplary apparatus employing theprinciples of the invention as illustrated in the accompanying drawings,in which:

FIG. 1 depicts a preferred embodiment of a directional drilling toolarranged in accordance with the principles of the present invention asit may appear while drilling a borehole;

FIG. 2 is a cross-sectioned elevational view of the more-significantportions of the tool illustrated in FIG. I;

FIGS. 4 and 5 are views similar to FIG. 2 but respectively illustratesuccessive operating positions of various control elements of thedirectional drilling tool during the course of a typical operation.

Turning now to FIG. I, a directional drilling tool 10 dependcntlycoupled from the lower end of a typical tubular drill string 11 is shownas it may appear during the course ofthc cxcavation of a borehole 12. Atypical drill bit 13 is operatively arranged on the lower end of thedirectional drilling tool 10 for operation in the usual manner uponrotation of the drill string 11 by a typical drilling rig (not shown) atthe surface.

As illustrated in FIGS. 1 and 2, the directional drilling tool 10 has anelongated, thick-walled tubular body 14 with an axial bore 15therethrough to accommodate the usual circulation of drilling fluids orso-called mud" from the surface through the drill string 11 andappropriate discharge openings (not shown) in the drill bit 13 and backto the surface by way of the borehole l2. Pressure-actuated guidingmeans 16 are mounted on a lower portion of the tool body 14 andoperatively connected by selectively-operable control means 17 topressure-developing means 18 arranged thereabove on the tool and adaptedfor selectively developing fluid pressures for actuation of the guidingmeans.

As best seen in FIG. 2, the guiding means 16 preferably include one ormore laterally movable pistons 19 that are respectively disposed inoutwardly opening radial bores 20 arranged along one side of an annularmember 21 that is movable mounted around the tool body 14 betweenlongitudinally spaced opposed shoulders 22 and 23 thereon. To enable theannular member 21 to slide longitudinally in relation to the tool body14, the shoulders 22 and 23 are spaced from the ends of the annularmember. A compression spring 24 is, however, engaged between the lowershoulder 23 and the annular member 21 to normally position the annularmember against the upper shoulder 22. For reasons that will subsequentlybe explained, opposed clutch members, such as one or more coengageableteeth 25 and 26, are respectively arranged on the lower end of theannular member 21 and the upwardly directed shoulder 23 therebelow forcorotatively securing the annular member to the body 14 whenever theannular member and lower shoulder are brought together. It will benoted, however, that the spring 24 normally urges the upper end of theannular member 21 against the downwardly directed shoulder 22 so thatthe annular member is free to rotate in relation to the tool body 14.

To accommodate the lateral movements of the tool-guiding pistons 19, acircumferential recess 27 is formed around the tool body 14 and providesan adequate volumetric capacity for a suitable operating fluid such asoil or other hydraulic fluids (not shown) for properly actuating thepistons. Suitable sealing members, such as O-rings 28 and 29, aresealingly engaged between the tool body and the upper and lower ends,respectively, of the annular member to seal the annular space 27 definedbetween the body 14 and the movable member 21.

In the depicted preferred embodiment of the pressuredeveloping means 18,the internal bore 15 of the tool body 14 .is substantially enlarged, asat 30, and receives an annular piston 31 having a reduced-diametertubular guide 32 extending therebelow and slidably engaged with aslightly enlarged complementary portion 33 of the internal bore. Sealingmembers 34 and 35 are suitably arranged around the piston 31 and itsdepending guide 32, respectively, for sliding engagement with theirassociated portions of the tool body 14 and define an enclosed chamber36 for containing a supply of the operating or hydraulic fluid. Springmeans, such as one or more Bellville washers 37 coaxially disposedaround the depending tubular portion 32, are operatively arranged in thepiston chamber 36 for normally urging the piston 31 upwardly against anopposed body shoulder 38 defining the upper limit of the enlarged boreportion 30. It should be noted that the pressure of fluids in thelongitudinal bore 15 will impose a corresponding downward force on theupper face of the piston 31.

Fluid communication is provided between the enclosed chambers 20 and 36by suitable passage means such as a body passage 39 coupling the lowerchamber to the lower end of an enlarged longitudinal bore 40 formedthereabove in the tool body 14 and having its upper end in communicationwith the upper chamber. As will subsequently be described in furtherdetail, the selectively-operable control means 17 are opera tivelyarranged in the enlarged longitudinal bore 40 and adapted forselectively communicating the pressure chambers 20 and 36 by certainoperations at the surface.

It will be appreciated from FIG. 2 that the pressure-developing piston31 will remain in its depicted position so long as the pressure of thecirculating fluids in the longitudinal bore 15 through the tool body 14is about equal to the hydrostatic pressure of the fluids in the borehole12. It is preferred that the upwardly acting spring force of theBellville washers 37 be selected so that at least a predeterminedincrease in the pressure of the circulating fluids in the longitudinalbore 15 will move the piston 31 downwardly. The operating fluids in thelower and upper piston chambers 20 and 366 will, of course, normally beat the hydrostatic pressure of the borehole fluids at whatever depth thetool then occupies. Thus, since the tool-guiding pistons 19 are normallyretracted, the pressure in the lower piston chamber 20 must be increasedabove the borehole pressure by developing an increased pressure in theupper piston chamber 36 to extend the tool-guiding pistons.

Those skilled in the art will, of course, recognize that during thecourse of typical drilling operations, the circulating fluids or mudmust be maintained at sufflcient pressures to achieve adequate fluidcirculation through the drilling bit 13 for removing formation cuttingsand transporting them upwardly in the borehole 12. Moreover, as thedrilling bit 13 encounters varying formation conditions, the fluidpressures required to maintain sufficient mud circulation will vary inaccordance with the formation conditions then being encountered.

Accordingly, the control means 17 for the tool 10 of the presentinvention are operatively arranged for selectively controllingcommunication between the piston chambers 20 and 36 without beinginadvertently operated by variations in the pressure of the drillingfluids circulating through the tool. In the preferred manner ofaccomplishing this, a tubular valve body 41 is sealingly mounted in theupper portion of the enlarged longitudinal bore 40 and dependentlycarries, as by threads 42, an elongated cylindrical body 43 of a smallerdiameter extending therebelow into the lower portion of the longitudinalbore. As depicted in FIG. 2, the upper end of the cylindrical body 43 iscoaxially arranged within the lower end of the valve body 41 to providean annular flow restriction 44 between the axial bore 45 of the valvebody and one or more longitudinal grooves 46 formed around the exteriorof the extension and opening into the lower portion of the longitudinalbore 40. An enlarged-diameter valve member 46 is operatively arrangedwithin the axial bore 45 of the valve body 41 for sliding movementtherein between the depicted elevated fluidblocking position and a lowerfluid-communicating position where the sealing member 47 mounted aroundthe valve member is disposed within an enlarged portion 48 of the axialbore. To guide the upward and downward movements of the valve member 46,an axial control rod 49 is dependently supported below the valve memberand coaxially arranged within an axial bore 50 in the cylindrical body43 which preferably terminatesjust above the lower end ofthe body.

Accordingly, as will be appreciated from FIG. 2, the valve member 46 andthe upper axial bore 45 in the tubular body 41 are operativelyproportioned to block fluid communication between the piston chambers 20and 36 until the valve member has traveled downwardly a sufficientdistance to bring the sealing member 47 into the enlarged-diameter bore48 in the tubular valve body. Once, however, the valve member 46 reachesthe enlarged bore 48, communication will be established between thepiston chambers 20 and 36 by way of the reduced annular restriction 44,the annular clearance between the cylindrical body 43 and the internalwall of the enlarged-diameter bore 40, and the fluid passage 39.

It will, of course, be appreciated that upon an increased fluid pressureof the circulating fluids in the longitudinal bore 15, the resultingdownward movement of the pressuredeveloping piston 31 will develop acorrespondingly increased fluid pressure in the upper piston chamber 36that will be effective for shifting the valve member 46 downwardly inrelation to the valve body 41. Accordingly, in the preferred manner ofregulating the movements of the valve member 46, cam means are providedsuch as four steeply inclined, alternately directed grooves 51-54 formedat uniform intervals around the depending guide rod 49 to provide acontinuous alternating path around the rod in which a cam member or pin55 projecting inwardly from the body 43 is received. Thus, by beginningat any given point in any of the grooves 51-54, an uninterrupted, upwardand downward path can be traced by following the alternate changes indirection of the intercon nected grooves around the rod 49 and on backto the initial starting point.

As will be noted by examination of FIGS. 2, 4 and 5, two of the grooves51 and 52 are shorter than the other two grooves 53 and 54, and theseshorter grooves are joined to one another at their upper ends with theirlower ends respectively joining the lower ends of each of the longergrooves. In this manner, by confining the free end of the cam pin 55within the labryinthlike system of grooves 51-54, the valve member 46will be alternately halted at an intermediate fluid-blocking position(FIG. 4) and a lower fluid-communicationg position (FIG. 5) uponsuccessive downward movements of the valve member. By arranging thelower ends of the four grooves SI 54 to be at the same elevation on theguide rod 49, the valve member 46 will be returned to its elevatedfluid-blocking position (FIG. 2) each time the valve member is shiftedupwardly. It will, of course, be appreciated that as the valve member 46is successively moved upwardly and downwardly, the cam pin 55 willcooperate with the several cam grooves 51-54 to also progressivelyrotate the valve member about its longitudinal axis.

To better appreciate the operation of the tool 10 of the presentinvention, a schematic diagram is depicted in FIG. 3 of thepressure-developing piston 31, the tool-guiding pistons 19, and thecontrol means 17. As illustrated there, so long as thepressure-developing piston 31 remains in its elevated position, thevalve member 46 will remain in the reduced-diameter bore 45 so as toblock fluid communication between the lower and upper piston chambers 20and 36. On the other hand, whenever the pressure-developing piston 31 isurged downwardly by an increase in the pressure of the circulatingfluids flowing through the tool 10, the resulting increase in pressurewithin the upper chamber 36 will shift the valve member 46 downwardly toeither its intermediate fluid-blocking position or its lowerfluid-communicating position depending upon whether the cam pin 55 is inthe shorter groove 51 or in the longer groove 53. If, for example, thecam pin 55 is in the shorter inclined groove 51, the downward movementof the valve member 46 will be halted once the shoulder defined by thejunction of the upper ends of the two shorter grooves 51 and 52 engagesthe cam pin. At this point, the sealing member 47 on the valve member 46will still be sealingly engaged within the reduced-diameter bore 45 inthe upper portion of the tubular valve body 41 so as to continueblocking fluid communication between the lower and upper piston chambers20 and 36. On the other hand, whenever the cam pin 55 is confined in thelonger groove 53, downward movement of the pressure-developing piston 31will be effective for shifting the valve member 46 downwardly until theshoulder at the junction of the upper ends of the longer grooves 53 and54 engages the cam pin. Once this occurs, the lower face of the valvemember 46 will be adjacent to the lower end of the enlarged bore 48 inthe valve body 41.

It will, of course, be appreciated that upward movement of the valvemember 46 will be readily accomplished by simply reducing the pressurein the internal bore through the tool body 14 to the hydrostaticpressure in the borehole 12 so as to allowthe pressure-developing piston31 to be returned upwardly by the Bellville washers 37. Thus, as thepressuredeveloping piston 31 is returned upwardly, the pressure in thelower piston chamber will be reduced and the tool-guiding pistons 19will be returned inwardly by the hydrostatic pressure in the borehole 12acting thereon. The decreased pressure in the upper piston chamber 36will, of course, allow the valve member 46 to be returned upwardly untilit again contacts a stop member 56 at the upper end of the valve body41.

Accordingly, by aLternately raising the pressure of the cir culatingfluids in the tool 10 above the borehole hydrostatic pressure and thendecreasing this pressure to about the borehole hydrostatic pressure, thevalve member 46 will be successively moved downwardly and returnedupwardly. As previously explained, on alternate increases of thecirculating pressure, the valve member 46 will merely be shifteddownwardly to its intermediate fluid-blocking position; and, following areduction in the circulating pressure, the next increase in circulatingpressure will be effective for shifting the valve member downwardly toits lower fluid-communicating position. i

It will be appreciated that once the seal 47 on the enlarged valvemember 46 begins to enter the enlarged bore 48 in the valve body 41, theincreased fluid pressure thereabove will tend to decrease as fluidcommunication is established with the lower piston chamber 20. Thus,should the pressure be substantially equalized across the enlarged valvemember 46, further downward travel of the valve member to itsfluid-communicating position would usually cease. This would, however,not allow the valve member 46 to move a sufficient distance downwardlyto enable the cam pin 55 to enter the next adjacent one of the camgrooves 51-54 whenever the circulating pressure is again reduced. As aresult, even though the valve member 46 would be returned upwardly by asubsequent reduction of fluid pressure in the internal tool bore 15, thenext increase of the circulating pressure would simply repeat the cycleso that the valve member would merely shift part way back and forthbetween its elevated position and its fully opened position. This would,of course, not allow the valve member 46 to be sequentially opened andclosed in the desired manner of operation of the tool 10.

Accordingly, to assure that the valve member 46 will be stroked its fullextent of travel each time it is moved toward its lowerfluid-communicating position, a flow restriction or orifice is arrangedbetween the enlarged bore 48 and the flow passage 39. The narrow orrestricted annular clearance space 44 defined between the coaxiallyarranged members 41 and 43 is, therefore, the preferred manner ofproviding this flow restriction. It will be noted from FIG. 2 that oncethe pressured fluid passes from the enlarged bore 48 through therestricted annular clearance 44 and the longitudinal grooves 46, arelatively uninterrupted path is provided to the passage 39 therebelowby the annular space between the internal wall of the longitudinal bore40 and the exterior of the cylindrical body 43. As a result, as thevalve member 46 is being moved downwardly to its fluid-communicatingposition, the annular orifice 44 will prevent a significant increase influid pressure in the longitudinal bore 40 below the orifice as thesealing member 47 first enters the enlarged bore 48. Thus, the annularflow restriction 44 will maintain an effective pressure dif ferentialacting on the upper face of the valve member 46 which will be sufficientfor moving the valve member completely downwardly until the cam pin 55has come to reset on the downwardly directed shoulder formed at theupper junction of the grooves 53 and 54.

It will, of course, be appreciated that as the valve member 46 is beingreelosed and reaches its intermediate fluidblocking position, furtherfluid communication is blocked between the lower and upper pistonchambers 20 and 36.

Thus, to provide a bypass around the valve member 46 for the hydraulicfluid in the lower piston chamber 20 to return to the upper pistonchamber 36 so that the toolguiding pistons 19 can be fully retracted, acheck valve assembly 57 is mounted in the enlarged head 46 and coupledby means of suitable passages as at 58 and 59 for permitting the flow ofhydraulic fluid between the enlarged bore portion 48 and the upperpiston chamber 36 but preventing flow in the opposite direction.

Once the valve member 46 is in its fluid-communicating position, inwardmovements of the tool-guiding pistons 19 will, of course, developcorresponding increased pressures in the lower piston chamber 20 tendingto reclose the valve member. Although the valve member 46 has aconsiderable travel span before it recloses the reduced bore 45, it isnevertheless preferred to dampen any momentary pressure differentialtending to reclose the valve member. Accordingly, in the preferredmanner of accomplishing this, a fluid restrictor such as one or moreserially arranged orifices or chokes 60 and passages 61 are provided topermit fluid communication between the passage 39 and the internal bore50 of the cylindrical member 43 below the lowermost position of theguide rod 49. In this manner, a momentary increase of the fluid pressurein the fluid passage 39 that would otherwise tend to elevate the valvemember 46 will be at least partially dampened by the orifices 60.

It will, of course, be appreciated that to facilitate the downwardmovement of the valve member 46, fluids trapped in the reduced bore 50below the lower end of the guide rod 49 should be rapidly exhausted tomaintain a substantial pressure differential that is effective formoving the valve member downwardly to its fluid-communicating positionbefore the fluid pressure across the annular orifice 44 has equalized.The orifices 60 will, however, tend to limit the rate at which thesetrapped fluids can be exhausted. Accordingly, a second check valveassembly 62 is mounted in the lower end of the cylindrical body 43 andoperatively arranged therein in parallel with the orifices 60 forreadily opening to permit fluid flow only from the bore 50 to the flowpassage 39.

Return of the valve member 46 from either of its two lower positions toits uppermost position is, of course, accomplished upon reduction of thecirculating pressure in the internal bore 15 of the tool 10. Thus, bysimply reducing the pressure in the internal bore 15 to about thehydrostatic pressure of the fluids in the borehole 12, thepressure-developing piston 31 will be returned upwardly by the Bellvillewashers 37 to its position as illustrated in FIG. 2. The upward movementof the pressuredeveloping piston 31 will, of course, create a momentarypressure reduction within the upper piston camber 36 so that thehydrostatic pressure acting on the tool-guiding pistons 19 will shiftthe valve member 46 upwardly by virtue of the increased pressure on thelowermost end of the depending guide rod 49. As previously described,although the check valve assembly 62 will not permit fluid to flow intothe internal bore 50 from the passageway 39, the orifices 60 in parallelwith the check valve assembly will admit fluid from the passageway intothe internal bore at a sufficient rate to assure that the valve member46 is fully reelosed and that the cam pin 55 is at the lower junction oftwo adjacent ones of the grooves 5154.

To employ the tool 10 of the present invention, a drill bit, such as at13 in FIG. 1, is coupled to the lower end of the tool and this assemblyis, in turn, dependently coupled to a drill string as at 11 which is, ofcourse, progressively assembled at the surface to lower the tool and thedrill bit into the borehole 12. Once the tool 10 reaches the bottom ofthe borehole 12 and the drilling fluids are being circulated through thedrill string 11, the pressure-developing piston 31 will be urgeddownwardly to develop an increased fluid pressure in the upper pistonchamber 36. As previously described, however, by orienting the valvemember 46 so as to position the shoulder at the upper junction of theshorter cam grooves 51 and 52 against the cam pin 55, the valve memberwill initially be in its intermediate fluid-blocking position (FIG. 4)and the tool-guiding pistons 19 will remain retracted. Accordingly,continued excavation of the borehole 12 can proceed in the usual mannerso long as the pistons 19 are retracted.

It will, of course, be appreciated that momentary reductions in thecirculating pressure will often occur such as, for example, when thecirculation of the drilling fluids is momentarily ceased to permitadditional lengths of pipe to be joined to the drill string 11. Aspreviously described, even such a momentary decrease in the circulatingfluid pressure will be effective for returning the valve member 46 toits fully elevated position (FIG, 2). As a result, when the circulationis again resumed, the valve member 46 will then be moved to itsfluid-communicating position (FIG To prevent the unwanted diversion ofthe drilling bit 13, the circulation of the drilling fluid must again bemomentarily reduced or halted to return the valve member 46 to itsuppermost position. Thereafter, upon resumption of the fluidcirculation, the valve member 46 will be repositioned in itsintermediate fluid-blocking position (FIG. 4) so that drilling cancontinue without the tool-guiding pistons 19 being extended.

Once it is determined that the drill bit 13 should be diverted in aselected direction in a accordance with the particular circumstances,the valve member 46 is deliberately actuated so as to shift it to itsfluid-communicating position. To accomplish this, since the valve member46 is in its intermediate fluid-blocking position, the fluid circulationis again momentarily ceased to restore the valve member to its elevatedposition (FIG. 2). Thereafter, upon resumption of the circulation, theincreased fluid pressure will be effective for shifting the valve member46 to its fully opened position (FIG. 5) and the tool-guiding pistons 19will be extended outwardly into contact with the walls of the borehole12.

It will, of course, be appreciated that the angular position of thetool-guiding pistons 19 in relation to the tool body 14 will not beknown since the annular member 21 is rotatably mounted on the tool body.Although other techniques can be employed to ascertain the angularposition of the tool-guiding pistons 19 in relation to the tool body 14,in one manner of determining this relationship, a typicalborehole-orienting device such as one of those shown on Pages l786-l793of the l968l969 Composite Catalog of Oil Field Equipment and Servicescan be lowered through the drill string 11 and alternately moved to oneposition for determining true north and then into another positionadjacent to the annular member 21 for detecting the angular position ofan indicator, such as, for example, a magnet 63 mounted on the annularmember 21 in a known angular position in relation to the toolguidingpistons 19. From successive readings of this nature, it will, therefore,be known how the pistons 19 are to be positioned to accomplish a desireddeviation of the bit 13. With a magnet, such as at 63, the annularmember 21 and at least the adjacent portions of the tool body 14 must,of course, be made of a suitable nonmagnetic material. Other means suchas downhole signaling devices associated with the tool can, of course,be arranged to provide the necessary signals at the surface forangularly positioning the member 21 and pistons 19.

Irrespective of the particular technique used to ascertain the angularposition of the tool-guiding pistons 19 in relation to the tool body 14,once this determination has been made, the drill string 11 is raisedsufficiently to coengage the opposed clutch teeth 25 and 26. lt will berecalled that, at this time, the tool-guiding pistons 19 are extended tosecure the annular member 21 and permit the tool body 14 to be movedupwardly in relation thereto. Once the clutch teeth 25 and 26 arecoengaged, the drill string 11 is rotated as required to position thetool-guiding pistons 19 at a selected angular position on the boreholewall. Although the pistons 19 are extended, sufficient torque can bereadily applied to the drill string 11 along with any necessaryreduction in circulating pressure to rotate the annular member 21 asrequired to move the toolguiding pistons to a desired angular positionin the borehole 12. Thereafter, once the drill string 11 is relowered todisengage the clutch teeth 25 and 26, further drilling will result inthe drill bit 13 being deviated away from the wall of the borehole 12against which the tool-guiding pistons 19 are then engaged.

It will be realized, of course, that each time the circulation of thedrilling fluid is ceased such as when an additional joint of pipe isadded to the drill string 11, the circulation pressure will have to bemomentarily increased and then temporarily halted before again beingraised to resume drilling so that the valve member 46 will again berestored to its fully open posi tion to maintain the tool-guidingpistons 19 firmly engaged against the wall of the borehole [2. Periodicor continuous checks can, of course, be made with suitabledirection-determining devices to determine the course of the drillingbit 13 and, if necessary, make further corrections to the angularposition of the tool-guiding pistons 19 in relation to the tool body 14.In any event, once the borehole 12 has been deviated sufficiently, thevalve member 46 can again be closed and then, if further drilling isnecessary, again moved to its intermediate fluid-blocking position toenable the resumption of drilling in the usual manner.

In any event, it will be appreciated that the present invention hasprovided a new and improved tool which is selectively operable forguiding a drill bit as it progressively excavates the borehole, withthis guidance being accomplished during the course of the drillingoperation without it being necessary to remove the drill string from theborehole to make corrective adjustments. By arranging thepressure-actuated guiding means 10 above the drill bit 13 forselectively deflecting it along a selected axis, the disclosed controlmeans 17 will permit the tool-guiding pistons 19 to be extended simplyby vary ing the pressure of the drilling fluids circulating through thedrill string 11.

While a particular embodiment of the present invention has been shownand described, it is apparent that changes and modifications may be madewithout departing from this invention in its broader aspects; and,therefore, the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope of thisinvention.

What 1 claim is:

1. Apparatus adapted for controlling the direction in which a boreholeis being excavated and comprising: a body adapted for connection in adrill string including a borehole-excavating device; pressure-developingmeans on said body and operable for developing increased pressures inresponse to selected changes in the pressures of fluids being circulatedthrough a drill string coupled to said body during the excavation of aborehole by a borehole-excavating device coupled thereto; wall-engagingmeans on said body and operable in response to increased pressuresapplied thereto for shifting said body laterally in relation to the axisof a borehole being excavated by a borehole-excavating device coupled tosaid body; and control means on said body and operable in response toselected changes in the pressures of such circulating fluids forselectively coupling said pressure-developing means to saidwall-engaging means for operation of said wall-engaging means.

2. The apparatus of claim 1 wherein said pressure-developing means areoperable in response to selected increases in the pressures of suchcirculating fluids.

3. The apparatus of claim 2 wherein said control means are operable inresponse to selected increases in the pressures of such circulatingfluids.

4. The apparatus of claim 1 wherein said control means include first andsecond pressure conduits respectively coupled to saidpressure-developing means and said guiding means, valve means adaptedfor movement relative to said body for selectively regulating pressurecommunication between said first and second conduits, andpressure-responsive actuating means coupled to said valve means andoperable in response to selected increases in the pressures of suchcirculating fluids for selectively moving said valve means to a positionfor establishing pressure communication between said first and secondconduits.

5. The apparatus of claim 4 wherein said valve means include a valvemember adapted for opening and closing pressure communication betweensaid first and second conduits upon movement of said valve memberbetween selected positions; and said actuating means include apressure-responsive actuating member operatively coupled to saidpressure developing means and adapted for moving said valve member toits said selected positions in response to predetermined changes in thepressures developed by said pressure-developing means.

6. The apparatus of claim 1 wherein said control means include first andsecond pressure conduits respectively coupled to said pressuredevelopingmeans and said guiding means, valve means adapted for movement relativeto said body for selectively regulating pressure communication betweensaid first and second conduits, means operatively arranged between saidvalve means and said body for alternately halting said valve means in afirst position blocking pressure communication between said first andsecond conduits upon a first movement of said valve means and haltingsaid valve means in a second position opening pressure communicationbetween said first and second conduits upon a second movement of saidvalve means, and pressure-responsive actuating means coupled betweensaid valve means and said pressure-developing means and operable inresponse to selected changes in the pressures developed by saidpressure-developing means for moving said valve means.

7. The apparatus of claim 6 wherein said pressure-develop ing means areoperable in response to selected increases in the pressures of suchcirculating fluids.

8. The apparatus of claim 7 wherein said pressure-responsive actuatingmeans are operable in response to alternate increases and decreases inthe pressures developed by said pressure-developing means.

9. A directional drilling tool comprising: an elongated body having alongitudinal circulating fluid passage therethrough and adapted forconnection in a rotating drill string including a borehole-excavatingdevice; wall-engaging means rotatably mounted on said body and includingat least a first piston operatively arranged in a first chamber forlateral movement between retracted and extended positions in relation tosaid body; pressure-developing means on said body in communication withsaid longitudinal passage and including a second piston operativelyarranged in a second chamber and adapted for movement from a firstposition to a second position in response to increases in the pressureof circulating fluids in said longitudinal passage for developingcorrespondingly increased pressures in a hydraulic fluid within saidsecond chamber; control means adapted for selectively intercoupling saidfirst and second pistons and including first and second conduitsrespectively coupled to said first and second chambers, valve meansmovably mounted on said body for movement between spaced positions andoperatively arranged for selectively regulating communication betweensaid first and second conduits in accordance with the position of saidvalve means, and valve-actuating means operable in response to selectedchanges in the pressure of such circulating fluids for selectivelymoving said valve means between said spaced positions; and clutch meansoperatively arranged between said wall-engaging means and said body forselectively securing said wall-engaging means in selected angularpositions on said body.

10. The directional drilling tool of claim 9 wherein saidvalve-actuating means include a pressure-responsive actuator, and athird conduit coupling said pressure-responsive actuator to said secondchamber for communicating increased pressures developed therein to saidpressure-responsive actuator for operating said valve means.

11. The directional drilling tool of claim 10 wherein said valve meansare movable between a first and a second one of said spaced positionsupon an increase of pressure in said second chamber for intercouplingsaid first and second chambers onl when said valve means are in saidsecond position; and sat valve-actuatmg means further include meansoperatively coupled to said valve means for alternately blockingmovement of said valve means to said second position and pennittingmovement of said valve means to said first position upon successiveincreases of pressure in said second chamber.

12. The directional drilling tool of claim 10 wherein said valve meansinclude a valve member operatively arranged on said body for movementrelative thereto between first, second and third ones of said spacedpositions and adapted for intercoupling said first and second chambersonly when said valve member is in its said third position; and saidactuating means include cam means operatively arranged between said bodyand said valve member for progressively indexing said valve member toeach of its said positions upon successive increases of pressure in saidsecond chambers.

13. The directional drilling tool of claim 10 wherein said valve meansinclude a valve member operatively arranged on said body for movementrelative thereto between first, second and third ones of said spacedpositions and adapted for intercoupling said first and second chambersonly when said valve member is in its said third position; and saidactuating means include cam means operatively arranged between said bodyand said valve member for progressively indexing said valve member toeach of its said positions upon successive cycles of an increase ofpressure in said second chamber followed by a decrease of pressuretherein.

1. Apparatus adapted for controlling the direction in which a boreholeis being excavated and comprising: a body adapted for connection in adrill string including a borehole-excavating device; pressure-developingmeans on said body and operable for developing increased pressures inresponse to selected changes in the pressures of fluids being circulatedthrough a drill string coupled to said body during the excavation of aborehole by a borehole-excavating device coupled thereto; wall-engagingmeans on said body and operable in response to increased pressuresapplied thereto for shifting said body laterally in relation to the axisof a borehole being excavated by a borehole-excavating device coupled tosaid body; and control means on said body and operable in response toselected changes in the pressures of such circulating fluids forselectively coupling said pressuredeveloping means to said wall-engagingmeans for operation of said wall-engaging means.
 2. The apparatus ofclaim 1 wherein said pressure-developing means are operable in responseto selected increases in the pressures of such circulating fluids. 3.The apparatus of claim 2 wherein said control means are operable inresponse to selected increases in the pressures of such circulatingfluids.
 4. The apparatus of claim 1 wherein said control means includefirst and second pressure conduits respectively coupled to saidpressure-developing means and said guiding means, valve means adaptedfor movement relative to said body for selectively regulating pressurecommunication between said first and second conduits, andpressure-responsive actuating means coupled to said valve means andoperable in response to selected increases in the pressures of suchcirculating fluids for selectively moving said valve means to a positionfor establishing pressure communication between said first and secondconduits.
 5. The apparatus of claim 4 wherein said valve means include avalve member adapted for opening and closing pressure communicationbetween said first and second conduits upon movement of said valvemember between selected positions; and said actuating means include apressure-responsive actuating member operatively coupled to saidpressure-developing means and adapted for moving said valve member toits said selected positions in response to predetermined changes in thepressures developed by said pressure-developing means.
 6. The apparatusof claim 1 wherein said control means include first and second pressureconduits respectively coupled to said pressure-developing means and saidguiding means, valve means adapted for movement relative to said bodyfor selectively regulating pressure communication between said first andsecond conduits, means operatively arranged between said valve means andsaid body for alternately halting said valve means in a first positionblocking pressure communication between said first and second conduitsupon a first movement of said valve means and halting said valve meansin a second position opening pressure communication between said firstand second conduits upon a second movement of said valve means, andpressure-responsive actuating means coupled between said valve means andsaid pressure-developing means and operable in response to selectedchanges in the pressures developed by said pressure-developing means formoving said valve means.
 7. The apparatus of claim 6 wherein saidpressure-developing means are operable in response to selected increasesin the pressures of such circulating fluids.
 8. The apparatus of claim 7wherein said pressure-responsive actuating means are operable inresponse to alternate increases and decreases in the pressures developedby said pressure-developing means.
 9. A directional drilling toolcomprising: an elongated body having a longitudinal circulating fluidpassage therethrough and adapted for connection in a rotating drillstring including a borehole-excavating device; wall-engaging meansrotatably mounted on said body and including at least a first pistonoperatively arranged in a first chamber for lateral movement betweenretracted and extended positions in relation to said body;pressure-developing means on said body in communication with saidlongitudinal passage and including a second piston operatively arrangedin a second chamber and adapted for movement from a first position to asecond position in response to increases in the pressure of circulatingfluids in said longitudinal passage for developing correspondinglyincreased pressures in a hydraulic fluid within said second chamber;control means adapted for selectively intercoupling said first andsecond pistons and including first and second conduits respectivelycoupled to said first and second chambers, valve means movably mountedon said body for movement between spaced positions and operativelyarranged for selectively regulating communication between said first andsecond conduits in accordance with the position of said valve means, andvalve-actuating means operable in response to selected changes in thepressure of such circulating fluids for selectively moving said valvemeans between said spaced positions; and clutch means operativelyarranged between said wall-engaging means and said body for selectivelysecuring said wall-engaging means in selected angular positions on saidbody.
 10. The directional drilling tool of claim 9 wherein saidvalve-actuating means include a pressure-responsive actuator, and athird conduit coupling said pressure-responsive actuator to said secondchamber for communicating increased pressures developed therein to saidpressure-responsive actuator for operating said valve means.
 11. Thedirectional drilling tool of claim 10 wherein said valve means aremovable between a first and a second one of said spaced positions uponan increase of pressure in said second chamber for intercoupling saidfirst and second chambers only when said valve means are in said secondposition; and said valve-actuating means further include meansoperatively coupled to said valve means for alternately blockingmovement of said valve means to said second position and permittingmovement of said valve means to said first position upon successiveincreases of pressure in said second chamber.
 12. The directionaldrilling tool of claim 10 wherein said valve means include a valvemember operatively arranged on said body for movement relative theretobetween first, second and third ones of said spaced positions andadapted for intercoupling said first and second chambers only when saidvalve member is in its said third positIon; and said actuating meansinclude cam means operatively arranged between said body and said valvemember for progressively indexing said valve member to each of its saidpositions upon successive increases of pressure in said second chambers.13. The directional drilling tool of claim 10 wherein said valve meansinclude a valve member operatively arranged on said body for movementrelative thereto between first, second and third ones of said spacedpositions and adapted for intercoupling said first and second chambersonly when said valve member is in its said third position; and saidactuating means include cam means operatively arranged between said bodyand said valve member for progressively indexing said valve member toeach of its said positions upon successive cycles of an increase ofpressure in said second chamber followed by a decrease of pressuretherein.